Search Results (4)

The degradation of bromothymol blue (BTB) in aqueous solution was investigated through individual and sequential photochemical and enzymatic treatments. Photodegradation experiments were performed under UVC, UVB, UVA and visible irradiation at different pH values and atmosphere conditions, while enzymatic degradation was evaluated using Laccase from Trametes versicolor under varying pH, temperature and enzyme concentration. Kinetic analyses were performed in all cases. BTB degradation was strongly dependent on irradiation wavelength and pH. The highest photodegradation rates were obtained under UVC irradiation, particularly in alkaline medium. Additionally, our results suggest that BTB photolysis mainly proceeds through a unimolecular pathway. On the other hand, enzymatic degradation was favored at acidic pH, elevated temperature, and high amount of laccase, with optimal performance observed at pH 5 and 40 °C. Sequential treatments combining photochemical and enzymatic processes improved the overall removal efficiency, reaching degradation values above 70% regardless of the treatments order. Ecotoxicological evaluation using the Vibrio fischeri bioluminescence inhibition assay revealed a significant reduction in toxicity after all treatments, particularly those involving UVC irradiation. These results demonstrate the complementary nature of both processes and highlight the potential of combined photochemical–enzymatic treatments for the remediation of dye-contaminated waters. Full article

Trace concentrations of dyes are often present in textile wastewater streams and present a serious environmental problem. Thus, these dyes must be removed from wastewater either by degradation or sequestration prior to discharge of the wastewater into the environment. Existing processes to remove these wastewater contaminants include the use of solid sorbents to sequester dyes or the use of biochemical or chemical methods of dye degradation. However, these processes typically generate their own waste products, are not necessarily rapid because of the low dye concentration, and often use expensive or non-recyclable sequestrants or reagents. This paper describes a simple, recyclable, liquid–liquid extraction scheme where ionic dyes can be sequestered into poly(α-olefin) (PAO) solvent systems. The partitioning of anionic and cationic dyes from water into PAOs is facilitated by ionic PAO-phase anchored sequestering agents that are readily prepared from commercially available vinyl-terminated polyisobutylene (PIB). This is accomplished by a sequence of reactions involving hydroboration/oxidation, conversion of an alcohol into an iodide, and conversion of the resulting primary alkyl iodide into a cationic nitrogen derivative. The products of this synthetic sequence are cationic nitrogen iodide salts which serve as anionic sequestrants that are soluble in PAO. These studies showed that the resulting series of cationic PIB-bound cationic sequestering agents facilitated efficient extraction of anionic, azo, phthalein, and sulfonephthalein dyes from water into a hydrocarbon PAO phase. Since the hydrocarbon PAO phase is completely immiscible with water and the PIB derivatives are also insoluble in water, neither the sequestration solvent nor the sequestrants contaminate wastewater. The effectiveness and efficiency of these sequestrations were assayed by UV–visible spectroscopy. These spectroscopic studies showed that extraction efficiencies were in most cases >99%. These studies also involved procedures that allowed for the regeneration and recycling of these PAO sequestration systems. This allowed us to recycle the PAO solvent system for at least 10 sequential batch extractions where we sequestered sodium salts of methyl red and 4′,5′-dichlorofluorescein dyes from water with extraction efficiencies of >99%. These studies also showed that a PIB-bound derivative of the sodium salt of 1,1,1-trifluoromethylpentane-2,4-dione could be prepared from a PIB-bound carboxylic acid ester by a Claisen-like reaction and that the sodium salt of this β-diketone could be used to sequester cationic dyes from water. This PIB-bound anion rapidly and efficiently extracted >99% of methylene blue, malachite green, and safranine O from water based on UV–visible and ¹H NMR spectroscopic assays. Full article

Isopropylmethylphenols, namely thymol and carvacrol, are natural phenolic monoterpenoids with a wide spectrum of bioactivity making them applicable in the cosmetic, pharmaceutical, and food industry. The dose-dependent antioxidant properties of isopropylmethylphenols require their quantification in real samples. Glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and electropolymerized thymolphthalein has been developed for the sensitive quantification of isopropylmethylphenols. Conditions of thymolphthalein electropolymerization (monomer concentration, number of cycles, and electrolysis parameters) providing the best response to thymol have been found. Scanning electron microscopy and electrochemical methods confirm the effectivity of the electrode developed. The linear dynamic ranges of 0.050–25 and 25–100 µM for thymol and 0.10–10 and 10–100 µM for carvacrol with detection limits of 0.037 and 0.063 µM, respectively, have been achieved in differential pulse mode in Britton–Robinson buffer pH 2.0. The selectivity of the isopropylmethylphenols response in the presence of typical interferences (inorganic ions, saccharides, ascorbic acid) and other phenolics (caffeic, chlorogenic, gallic and rosmarinic acids, and quercetin) is a significant advantage over other electrochemical methods. The electrode has been used in the analysis of oregano and thyme spices. Total isopropylmethylphenols contents have been evaluated after a single sonication-assisted extraction with methanol. Full article

Thymol and carvacrol (isopropylmethylphenols) are natural phenolic monoterpenoids with antibacterial, antifungal, insecticidal, and antioxidant properties. Their dose-dependent antioxidant effect requires control in real samples. Various modes of voltammetry have been successfully developed for thymol and carvacrol quantification. A glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and electropolymerized thymolphthalein has been developed for this purpose. The conditions of thymolphthalein electropolymerization (monomer concentration, number of cycles, and parameters of electrolysis) providing the best response to thymol have been found. The scanning electron microscopy and electrochemical methods confirm the effectivity of the sensor developed. In differential pulse mode, the sensor gives a linear response in the ranges of 0.050–25 and 25–100 μM for thymol and 0.10–10 and 10–100 μM for carvacrol, with detection limits of 0.037 and 0.063 μM, respectively, that are significantly improved compared to those reported earlier. The sensor developed is selective to isopropylmethylphenols in the presence of typical interferences (inorganic ions, saccharides, and ascorbic acid) and other phenolics (caffeic, chlorogenic, gallic and rosmarinic acids, quercetin, and rutin). A sensor has been applied for the evaluation of total isopropylmethylphenols in oregano and thyme spices using single sonication-assisted extraction with methanol. The voltammetric sensor data agreed well with the independent spectrophotometric quantification. Full article